Clock speeds are useless when comparing different architectures. The Ivy Bridge architecture is newer and a lot faster than the K10 architecture of the Phenom II. The price difference is fully justified.
The only point in favor of the Phenom II is that it can be overclocked freely.
So the amd processor is like $80 less than the intel one. Yet it has higher clock speed and it's quad core?
Why? Is the AMD one much slower in reality? I'm asking since I see several AMD processors much cheaper than intel ones. Are AMD ones slower?
Which one would have better performance gaming?
the i5 is a much faster cpu in general. though "much faster" is largely subjective. from an end user perspective, without a stopwatch it's doubtful you could tell which is powering a which pc if they were running next to each other. it would onyl become evident in extremely cpu intensive activities... such as encoding video or unzipping huge files, or with certain games at certain resolutions.
the PhII is playable and serviceable, but if you need an elite cpu to do advanced processing, it's not anywhere near as fast as an intel.